1. Field of the Invention
Fans, compressors, superchargers, blowers and the like all referred to herein generically as fans.
2. Brief Description of the Prior Art
It is desirable for fans to be uncomplicated, lightweight, economic, compact, durable and easily reparable, and to provide reliable, low stress, leak free, high efficiency performance. Many different designs are known that favor different ones of these objects in different proportions, including designs that utilize different rigid scroll and snail shell shaped housings. Prior rigid designs intended to provide high pressure, high flow rate, and/or high-efficiency performance are complex, expensive, and heavy. Thick rigid walls and/or extensive strut frames are used to contain the high pressures and flows, maintain sufficient tolerances to prevent leakage or back flow between the impeller and housing from the high pressure side of the impeller, prevent the impeller from striking the housing during operation, prevent vibration, and otherwise accommodate high-efficiency performance.
The prior art teaches that some cost and weight savings can be achieved by construction of a centrifugal fan with a cylindrical rotor disposed in an inflatable cylindrical scroll. But, the cylindrical configuration of the rotor and scroll limit the overall benefit of the design. A moderately extensive frame is required to prevent the scroll from falling into the rotor when the fan is not in operation, and to provide an effective flow path and good interconnection between the rotor section and outlet duct. There is only a limited reduction in volume and benefit for purposes such as shipment from one location to another when the fan is not in operation and the housing is deflated. And, the edges or corners of cylindrical housings produce uneven distributions of forces across the housing surfaces that generally either limit fan efficiency or require a sturdier construction than would otherwise be needed.